Studies on the phenomena associated with resitance of the Chinese hamster to Trichinella spiralis (muscle phase) are in progress. The non-resistant golden hamster is being used, where appropriate, as a comparative host in studies on responses to this infection. A preliminary survey of immune responses (humoral and cellular) of trichinella infected Chinese hamsters is to be concluded. Studies on the sequence of changes which occur in muscle following infection by trichinella are in progress. In this, the tissue phase of the parasite will be studied using an experimentally isolated portion of the parasite's cycle (i.e., tissue injection of juvenile worms). The effects of host manipulations (e.g., chloroquine. steroid, etc.) on the evolution of the infectious process will be determined using the same test system. Observations on the resistant Chinese hamster will be compared with the correspondingly infected/manipulated, non-resistant golden hamster.